A I have said, cancer is already something in our body, something we have a genetic possibility to develop. There are some things like alcohol or cigarrets, polution etc... that can help you develop it. Psychological tension or a problem not well resolved is one of them. I have even heard cases in which women who lost their children when they were just a few month old and refused accept that by having another kid to literally replaced the first one, developed cancer. Was it the only reason? is it the only cause? no. Things affect differectly to different people, you don't need to study psychology to know that. But is it a factor? DEF.